UK Anti-Doping claimed its 'jiffy bag' investigation could have been "potentially compromised" by British Cycling being slow to report allegations of doping.

British Cycling on Friday released letters sent between itself and UKAD in November despite the anti-doping agency last month refusing Freedom of Information requests to do so.

A letter sent by UKAD to British Cycling chief executive Julie Harrington on November 14 claimed the investigation was "hindered" by the organisation's failure to report the allegations immediately.

It read: "Despite being aware of the allegations in relation to the 2011 'package' British Cycling was slow to inform UKAD of these. In fact, contact on this matter was made at UKAD's instigation.

"Contact by British Cycling with some members of staff at British Cycling, prior to informing UKAD, could have potentially compromised our investigation with the possible loss of data evidence."

It added: "Failure to inform UKAD at the time that individuals within British Cycling became aware of such suspicions or allegations meant that this story had already reached a number of individuals before UKAD was informed and thus able to act. That only hindered our efforts."

UKAD spent 14 months investigating the claim that a mystery package delivered to a Team Sky doctor at a race in France in 2011 contained a banned corticosteroid and it was administered by the doctor, Richard Freeman, to star rider Sir Bradley Wiggins on the team bus, which would be a breach of the anti-doping rules.

Freeman, who recently resigned as British Cycling's medical chief, Wiggins and the team have all consistently denied any wrongdoing, and claimed the package actually contained a legal decongestant.

UKAD was forced in November to admit its investigation had stalled and there was no immediate prospect of any charges being brought, having been hampered by a lack of documentation to show the drug was dispatched from the medical storeroom Team Sky shared with British Cycling.

In the letter, UKAD also criticised British Cycling's records procedure, its "chaotic and disorganised" medical room and added that "we found little, if any, evidence of supervision or executive oversight of the team doctors by British Cycling".

In British Cycling's response, it admitted: "UKAD's findings represent an organisation and culture that, despite delivering on the world stage, did not meet the high standards to which British Cycling today holds itself."

A statement on its website added: "British Cycling has made a number of significant changes to the provision of medical services to the Great Britain cycling team. All of the recommendations of a review commissioned in April 2017 have been implemented. This review was in response to initial findings by UKAD given to the Culture, Media and Sport Select Committee in March 2017."